DNS policies
When a user makes a DNS request to Gateway, Gateway matches the request against the DNS policies you have set up for your organization. If the domain does not belong to any blocked categories, or if it matches an Override policy, the user’s client receives the DNS resolution and initiates an HTTP connection.
A DNS policy consists of an Action as well as a logical expression that determines the scope of the action. To build an expression, you need to choose a Selector and an Operator, and enter a value or range of values in the Value field. You can use And and Or logical operators to evaluate multiple conditions.
When creating a DNS policy, you can select as many security risk categories and content categories as needed to fully secure your network. Unless a more specific selector is configured in a policy (for example, User Email or Source IP), then the policy will be evaluated against all DNS queries that reach Gateway from your organization.
If a condition in an expression joins a query attribute (such as Source IP) and a response attribute (such as Resolved IP), then the condition will be evaluated when the response is received.
Actions
Just like actions in HTTP policies, actions in DNS policies allow you to choose what to do with a given set of elements. You can assign one action per policy.
These are the action types you can choose from:
Allow
API value: allow
Available selectors
Traffic
- Application
- Authoritative Nameserver IP
- Content Categories
- DNS CNAME Response Value
- DNS MX Response Value
- DNS PTR Response Value
- DNS Resolver IP
- DNS TXT Response Value
- DOH Subdomain
- Domain
- Host
- Indicator Feeds
- Location
- Query Record Type
- Resolved Continent IP Geolocation
- Resolved Country IP Geolocation
- Resolved IP
- Security Categories
- Source Continent IP Geolocation
- Source Country IP Geolocation
- Source IP
Identity
Policies with Allow actions allow DNS queries to reach destinations you specify within the Selector and Value fields. For example, the following configuration allows DNS queries to reach domains we categorize as belonging to the Education content category:
| Selector | Operator | Value | Action |
|---|---|---|---|
| Content Categories | in | Education | Allow |
Disable DNSSEC validation
When you select Disable DNSSEC validation, Gateway will resolve DNS queries even if the cryptographic signature for the DNS record cannot be validated. We do not recommend disabling DNSSEC validation unless you know that the validation failure is due to DNSSEC configuration issues and not malicious attacks.
Block
API value: block
Available selectors
Traffic
- Application
- Authoritative Nameserver IP
- Content Categories
- DNS CNAME Response Value
- DNS MX Response Value
- DNS PTR Response Value
- DNS Resolver IP
- DNS TXT Response Value
- DOH Subdomain
- Domain
- Host
- Indicator Feeds
- Location
- Query Record Type
- Resolved Continent IP Geolocation
- Resolved Country IP Geolocation
- Resolved IP
- Security Categories
- Source Continent IP Geolocation
- Source Country IP Geolocation
- Source IP
Identity
Policies with Block actions block DNS queries to reach destinations you specify within the Selector and Value fields. For example, the following configuration blocks DNS queries from reaching domains we categorize as belonging to the Adult Themes content category:
| Selector | Operator | Value | Action |
|---|---|---|---|
| Content Categories | in | Adult Themes | Block |
Custom block page
When choosing the Block action, turn on Display custom block page to respond to queries with a block page and to specify the message you want to display to users who go to blocked websites. If the block page is disabled, Gateway will respond to blocked queries with an A record of 0.0.0.0 for IPv4 destinations, or with an AAAA record of :: for IPv6 destinations. For more information, refer to the dedicated documentation on customizing the block page.
WARP client block notifications
Feature availability
| WARP modes | Zero Trust plans ↗ |
|---|---|
| Enterprise |
| System | Availability | Minimum WARP version |
|---|---|---|
| Windows | ✅ | 2024.1.159.0 |
| macOS | ✅ | 2024.1.160.0 |
| Linux | ❌ | |
| iOS | ✅ | 1.7 |
| Android | ✅ | 1.4 |
| ChromeOS | ✅ | 1.4 |
Turn on Display block notification for WARP client to display notifications for Gateway block events. Blocked users will receive an operating system notification from the WARP client with a custom message you set. If you do not set a custom message, the WARP client will display a default message. Custom messages must be 100 characters or less.
Upon selecting the notification, WARP will direct your users to a block page. Optionally, you can direct users to a custom URL, such as an internal support form.
To turn on client notifications on macOS devices running DisplayLink software, you may have to allow system notifications when mirroring your display. For more information, refer to the macOS documentation ↗.
Override
API value: override
Available selectors
The Override action cannot be used with selectors evaluated during or after DNS resolution.
Traffic
- Application
- Content Categories
- DNS Resolver IP
- DOH Subdomain
- Domain
- Host
- Location
- Query Record Type
- Resolved Continent IP Geolocation
- Resolved Country IP Geolocation
- Security Categories
- Source Continent IP Geolocation
- Source Country IP Geolocation
- Source IP
Identity
Policies with Override actions allow you to respond to all DNS queries for a given domain to another destination. For example, you can provide a custom response IP of 1.2.3.4 for all queries to www.example.com with the following policy:
| Selector | Operator | Value | Action | Override Hostname |
|---|---|---|---|---|
| Hostname | is | www.example.com | Override | 1.2.3.4 |
Safe Search
API value: safesearch
Available selectors
Traffic
- Application
- Content Categories
- DNS Resolver IP
- DOH Subdomain
- Domain
- Host
- Location
- Query Record Type
- Resolved Continent IP Geolocation
- Resolved Country IP Geolocation
- Security Categories
- Source Continent IP Geolocation
- Source Country IP Geolocation
- Source IP
Identity
SafeSearch is a feature of search engines that helps you filter explicit or offensive content. When you enable SafeSearch, the search engine filters explicit or offensive content and returns search results that are safe for children or at work.
You can use Cloudflare Gateway to enable SafeSearch on search engines like Google, Bing, Yandex, YouTube and DuckDuckGo. For example, to enable SafeSearch for Google, you can create the following policy:
| Selector | Operator | Value | Action |
|---|---|---|---|
| Domain | is | google.com | Safe Search |
YouTube Restricted Mode
API value: ytrestricted
Available selectors
Traffic
- Application
- Content Categories
- DNS Resolver IP
- DOH Subdomain
- Domain
- Host
- Location
- Query Record Type
- Resolved Continent IP Geolocation
- Resolved Country IP Geolocation
- Security Categories
- Source Continent IP Geolocation
- Source Country IP Geolocation
- Source IP
Identity
Similarly, you can enforce YouTube Restricted mode by choosing the YouTube Restricted action. YouTube Restricted Mode is an automated filter for adult and offensive content built into YouTube. To enable YouTube Restricted Mode, you could set up a policy like the following:
| Selector | Operator | Value | Action |
|---|---|---|---|
| DNS Domain | is | youtube.com | YouTube Restricted |
This setup ensures users will be blocked from accessing offensive sites using DNS.
Selectors
Gateway matches DNS queries against the following selectors, or criteria:
Application
You can apply DNS policies to a growing list of popular web applications. Refer to Application and app types for more information.
| UI name | API example | Evaluation phase |
|---|---|---|
| Application | any(app.ids[*] in {505}) | Before DNS resolution |
Authoritative Nameserver IP
Use this selector to match against the IP address of the authoritative nameserver IP address.
| UI name | API example | Evaluation phase |
|---|---|---|
| Authoritative Nameserver IP | dns.authoritative_ns_ips == 198.51.100.0 | During DNS resolution |
Content Categories
Use this selector to filter domains belonging to specific content categories.
| UI name | API example | Evaluation phase |
|---|---|---|
| Content Categories | any(dns.content_category[*] in {1}) | Before DNS resolution |
When using an Allow or Block action, you can optionally block IP addresses or filter categories for CNAME records.
DNS CNAME Record
Use this selector to filter DNS responses by their CNAME records.
| UI name | API example | Evaluation phase |
|---|---|---|
| DNS CNAME Response Value | any(dns.response.cname[*] in {"www.apple.com.edgekey.net"}) | After DNS resolution |
DNS MX Record
Use this selector to filter DNS responses by their MX records.
| UI name | API example | Evaluation phase |
|---|---|---|
| DNS MX Response Value | any(dns.response.mx[*] in {"gmail-smtp-in.l.google.com"}) | After DNS resolution |
DNS PTR Record
Use this selector to filter DNS responses by their PTR records.
| UI name | API example | Evaluation phase |
|---|---|---|
| DNS PTR Response Value | any(dns.response.ptr[*] in {"255.2.0.192.in-addr.arpa"}) | After DNS resolution |
DNS Resolver IP
Use this selector to apply policies to DNS queries that arrived to your Gateway Resolver IP address aligned with a registered DNS location. For most Gateway customers, this is an IPv4 anycast address and policies created using this IPv4 address will apply to all DNS locations. However, each DNS location has a dedicated IPv6 address and some Gateway customers have been supplied with a dedicated IPv4 address — these both can be used to apply policies to specific registered DNS locations.
| UI name | API example | Evaluation phase |
|---|---|---|
| DNS Resolver IP | any(dns.resolved_ip[*] == 198.51.100.0) | Before DNS resolution |
DNS TXT Record
Use this selector to filter DNS responses by their TXT records.
| UI name | API example | Evaluation phase |
|---|---|---|
| DNS TXT Response Value | any(dns.response.txt[*] in {"your_text"}) | After DNS resolution |
DoH Subdomain
Use this selector to match against DNS queries that arrive via DNS-over-HTTPS (DoH) destined for the DoH endpoint configured for each DNS location. For example, you can use a DNS location with a DoH endpoint of abcdefg.cloudflare-gateway.com by choosing the DoH Subdomain selector and inputting a value of abcdefg.
| UI name | API example | Evaluation phase |
|---|---|---|
| DOH Subdomain | dns.doh_subdomain == "abcdefg" | Before DNS resolution |
Domain
Use this selector to match against a domain and all subdomains. For example, you can match example.com and its subdomains, such as www.example.com.
| UI name | API example | Evaluation phase |
|---|---|---|
| Domain | any(dns.domains[*] == "example.com") | Before DNS resolution |
Host
Use this selector to match against only the hostname specified. For example, you can match test.example.com but not example.com or www.test.example.com.
| UI name | API example | Evaluation phase |
|---|---|---|
| Host | dns.fqdn == "test.example.com" | Before DNS resolution |
Indicator Feeds
Use this selector to match against custom indicator feeds.
You can use a publicly available indicator feed or a custom indicator feed assigned to your account by a designated third-party vendor. For more information on indicator feeds, refer to Custom Indicator Feeds.
| UI name | API example | Evaluation phase |
|---|---|---|
| Indicator Feeds | dns.indicator_feed | Before DNS resolution |
Location
Use this selector to apply policies to a specific Gateway DNS location or set of locations.
| UI name | API example | Evaluation phase |
|---|---|---|
| Location | dns.location in {"location_uuid_1" "location_uuid_2"} | Before DNS resolution |
Query Record Type
Use this selector to choose the DNS resource record type that you would like to apply policies against. For example, you can match A records for a domain but not MX records.
| UI name | API example | Evaluation phase |
|---|---|---|
| Query Record Type | dns.query_rtype == "TXT" | Before DNS resolution |
Resolved Continent
Use this selector to filter based on the continent that the query resolves to. Geolocation is determined from the IP address in the response. To specify a continent, enter its two-letter code into the Value field:
- AF – Africa
- AN – Antarctica
- AS – Asia
- EU – Europe
- NA – North America
- OC – Oceania
- SA – South America
- T1 – Tor network
| UI name | API example | Evaluation phase |
|---|---|---|
| Resolved Continent IP Geolocation | dns.dst.geo.continent == "EU" | After DNS resolution |
Resolved Country
Use this selector to filter based on the country that the query resolves to. Geolocation is determined from the IP address in the response. To specify a country, enter its ISO 3166-1 Alpha 2 code ↗ in the Value field.
| UI name | API example | Evaluation phase |
|---|---|---|
| Resolved Country IP Geolocation | dns.dst.geo.country == "RU" | After DNS resolution |
Resolved IP
Use this selector to filter based on the IP addresses that the query resolves to.
| UI name | API example | Evaluation phase |
|---|---|---|
| Resolved IP | any(dns.resolved_ips[*] == 198.51.100.0) | After DNS resolution |
Security Categories
Use this selector to match domains (and optionally, IP addresses) belonging to specific security categories.
| UI name | API example | Evaluation phase |
|---|---|---|
| Security Categories | any(dns.security_category[*] in {1}) | Before DNS resolution |
When using an Allow or Block action, you can optionally block IP addresses or filter categories for CNAME records.
Source Continent
Use this selector to filter based on the continent where the query arrived to Gateway from.
Geolocation is determined from the device’s public IP address (typically assigned by the user’s ISP). To specify a continent, enter its two-letter code into the Value field:
| Continent | Code |
|---|---|
| Africa | AF |
| Antarctica | AN |
| Asia | AS |
| Europe | EU |
| North America | NA |
| Oceania | OC |
| South America | SA |
| Tor network | T1 |
| UI name | API example | Evaluation phase |
|---|---|---|
| Source Continent IP Geolocation | dns.src.geo.continent == “North America” | Before DNS resolution |
Source Country
Use this selector to filter based on the country where the query arrived to Gateway from.
Geolocation is determined from the device’s public IP address (typically assigned by the user’s ISP). To specify a country, enter its ISO 3166-1 Alpha-2 code ↗ in the Value field.
| UI name | API example | Evaluation phase |
|---|---|---|
| Source Country IP Geolocation | dns.src.geo.country == “RU” | Before DNS resolution |
Source IP
Use this selector to apply policies to the source IP address of DNS queries. For example, this could be the WAN IP address of the stub resolver used by your organization to send queries to Gateway.
| UI name | API example | Evaluation phase |
|---|---|---|
| Source IP | dns.src_ip == 198.51.100.0 | Before DNS resolution |
Users
Identity-based selectors include:
- SAML Attributes
- User Email
- User Group Emails
- User Group IDs
- User Group Names
- User Name
To use identity-based selectors, enable Gateway with WARP in the Zero Trust WARP client and enroll your user in your organization. For more information, refer to Identity-based policies.
Comparison operators
Comparison operators are the way Gateway matches traffic to a selector. When you choose a Selector in the dashboard policy builder, the Operator dropdown menu will display the available options for that selector.
| Operator | Meaning |
|---|---|
| is | equals the defined value |
| is not | does not equal the defined value |
| in | matches at least one of the defined values |
| not in | does not match any of the defined values |
| in list | in a pre-defined list of values |
| not in list | not in a pre-defined list of values |
| matches regex | regex evaluates to true |
| does not match regex | regex evaluates to false |
| greater than | exceeds the defined number |
| greater than or equal to | exceeds or equals the defined number |
| less than | below the defined number |
| less than or equal to | below or equals the defined number |
Value
In the Value field, you can input a single value when using an equality comparison operator (such as is) or multiple values when using a containment comparison operator (such as in). Additionally, you can use regular expressions (or regex) to specify a range of values for supported selectors.
Regular expressions
Gateway uses Rust to evaluate regular expressions. The Rust implementation is slightly different than regex libraries used elsewhere. For more information, refer to our guide for Wildcards. To evaluate if your regex matches, you can use Rustexp ↗.
If you want to match multiple values, you can use the pipe symbol (|) as an OR operator. In Gateway, you do not need to use an escape character (\) before the pipe symbol. For example, the following policy blocks requests to two hostnames if either appears in a request header:
| Selector | Operator | Value | Action |
|---|---|---|---|
| Host | matches regex | .\*whispersystems.org|.\*signal.org | Block |
In addition to regular expressions, you can use logical operators to match multiple values.
Logical operators
To evaluate multiple conditions in an expression, select the And logical operator. These expressions can be compared further with the Or logical operator.
| Operator | Meaning |
|---|---|
| And | match all of the conditions in the expression |
| Or | match any of the conditions in the expression |
The Or operator will only work with conditions in the same expression group. For example, you cannot compare conditions in Traffic with conditions in Identity.
Limitations
Third-party filtering conflict
Gateway will not properly filter traffic sent through third-party VPNs or other Internet filtering software, such as iCloud Private Relay ↗. To ensure your DNS policies apply to your traffic, Cloudflare recommends turning off software that may interfere with Gateway.
To turn off iCloud Private Relay, refer to the Apple user guides for macOS ↗ or iOS ↗.
Magic WAN forwarding
To apply DNS policies to queries forwarded through Magic WAN, you can either point your organization’s DNS resolver to an IPv6, DoH, or DoT endpoint or request a dedicated resolver IPv4 address. For more information, refer to DNS resolver IPs and hostnames.